36 



ANIMAL PHYSIOLOGY. 



bones, which contain the organs of hearing in their interior. 

 The part of the temporal which lies above the external audit- 

 ory meatus, or opening of the ear, is termed the squamous 

 portion; the thick process behind is called mastoid; the 

 pyramidal projection into the base is the petrous portion; 

 and a plate which forms the inferior limit of the opening of 

 the ear, and of the cavity into which it leads, is the tympanic 

 plate. Enclosed by this plate, within what is called the 

 tympanic cavity, are three little ossicles, which will be de- 

 scribed with the organ of hearing. 



Fig. 17. SKULL. A, Profile view. B, Vertical section, a, 

 occipital bone; &, parietal; c, frontal; d, squamous portion of 

 temporal ; e, mastoid portion ; /, petrous portion ; g t sphenoid ; 

 h, pterygoid process of sphenoid ; i, ethmoid ; &, nasal ; l y 

 superior maxillary ; m, pre -maxillary part of superior maxillary ; 

 n, palatal; o, malar; p, lachrymal; q, inferior maxillary; r, 

 inferior turbinated. _, - . 



19. Of the face bones, the largest is the inferior maxilla, or 

 lower jaw, and this is the only one which is movably artic- 

 ulated. The remaining part of the face consists mainly of 

 the walls of a passage, the interior of which is divided into 

 the right and left nasal fossae by a mesial bone called the 

 vomer, together with a mesial plate of the ethmoid. The 

 iloor of this passage constitutes the palate. Much the larger 

 part of this division of the face in the human subject is 

 formed by the superior maxillary bones, which carry all 

 the upper teeth, and represent two pairs of bones in the 



